The church I went too when I was a child hosted Christian rock shows from smallish artists. One of them was particularly mid, and after their last song everyone started to leave without a single person calling for encore. The band ran back out for their "scheduled encore" to a silent crowd and started playing another song while everyone left.
I think about how awkward that was every time I go to a show now.
In best encores, Porter Robinson played Cheerleader twice in a row for the Seattle show on his tour last year since it was going to be the last show with this big billboard on stage that they couldn't bring on the world tour, so he got all hooked back up in his harness and they played it again. The second go was more fantastic than the first.